Proceedmgs offhe First Asian-Australian Drying Conference (ADC99) Bali. Indonesia. 24-1"" October 1999
RECENT DEVELOPMENT OF GHE SOLAR DRYING IN
INDONESIA -GRASS ROOTS PROJECT
Kamaruddin Abdullah', Dyah W.2, L.O.Nelwan2 and L.P. ManaluJ 'Center for Research on Engineering Applications in Tropical Agriculture (CREATA-LP-IPB); Darmaga Campus ofIPB, Bogor, West
Java,Tel./Fax:+61-251-62188617 ;E-mai t: crea -i pbCu{i ndo. net.id;kdi n@bogor.wasantara.net.id
2 Graduate students, IPB Graduate Program
3 Researcher, Agency for the Assessment and Application of Technology (BPPT)
Key ｷｯｲ､ｳｾ＠ Green house effect, solar dryer, action research, tropical crops.
ABSTRACT
Study on greenhouse effect (GHE) solar dryer was initiated since early 1990's in our laboratory. From several test results conducted using different type of GHE solar dryers, it was found that such system was applicable to a wide variety of tropical products from grains such as black pepper, rough rice, coffee and cocoa beans, to seeds, timber and sHced fruits. The latest experiment with the GHE solar dryer using mechanical stirrer to dry fermented cocoa beans, for example, was capable to reduce the total specific energy (solar and commercial energy) from about 12 MJ/kg of moisture as reported elsewhere to 6.2 MJllcg moisture. For the case of coffee drying without any mixing device but with relatively high loading capacity the recorded specific energy was 5.5
MJIIcg
of moisture.Therefore, under the current stage of RID activity will be focused on the dissemination of appropriate GHE solar dryers through action research to promote the development of small scale industries in the rural areas so that they can help the farmers in processing their products. This paper presents some results of drying performance with GHE solar dryer including the introduction of several action
research program to disseminate the technology in Indonesia.
INTRODUCTION
After a long research and development effort at CREATA (Center for
Research on Engineering Applications in Tropical Agriculture) of IPB, some prototypes of renewable energy driven thennal systems are now ready for dissemination. The Greenhouse Effect (GHE) solar dryer, for example, was found to
be far less expensive than the conventional solar dryer using solar heat collector. Several types of drying bins had been tested namely, the stationery rectangular bin,
vibrating racks, stationary racks, and cylindrical bin with mechanical stirrer. If such system can be applied in the eastern part of the country where solar radiation is high
I
I
In 1994 dissemination of the technology was initiated by applying the GHE system for seed drying. For the same purpose, since August 1998, a joint project with the Research and Development Center for Calibration, Instrumentation and Metrology of the Indonesian Institute of Sciences (LIPI), was started. In the latter undertaking two GHE solar dryers, one for coffee berry with 6 ton wet capacity and another having a capacity of 1 ton wet were installed in East Java and Sumbawa Island, respectively. The main objective of the project was to apply appropriate technology to help the people in the rural area to increase added value of their products and hence may lead to the improvement of economic condition in the area. Starting 1999, a grass roots project was granted by the government of Japan to install 4 GHE solar dryers one each in East Java and Bali and two in Sumbawa island. One of the dryer in Sumbawa is used to dry coffee berries.
This paper presents the results of laboratory as well as field tests of several models of a GHE solar dryer.
DESCRIPTION OF A GHE SOLAR DRYER
Previous study using Lagrange multiplier (Kamaruddin, 1993) have shown that the initial cOst of a solar drying system can be further reduced by using a greenhouse effect mechanism since the function of solar collector unit can be substituted by transparent structure which also simultaneously function as the drying chamber .. From structural and functional point of view a GHE solar drying system, as shown in Figure.l, is basically similar to a greenhouse. The entire wall is made of transparent materials such as fiberglass, UV stabilized plastic or polycarbonate sheets. The transparent sheets are fixed on steel frame support or pillars with bolts and nuts and rubber packing to prevent humid air leaking into the chamber other than those introduced from the inlet opening. A blackened steel plates is provided to enhanced solar radiation absorption within the structure and are located either on the upper section of the structure or at both sides near the wall. According to the type of commodity to be dried, the racks, cabinets or drying bin can be placed at the center section of the transparent structure so that maximum access to drying air can be obtained. Inlet and exhaust fan are placed at proper position within the structure to ensure even distribution of the drying air within the chamber. To reduce further the cost of air handling system a POID unit (Vo-Ngoc and Srivastava, 1993) can be
polycarbonate wall
Figurela. GHE solar dryer for cocoa bin
with
mechanical stirrer [image:3.539.73.457.389.644.2]Qel2 QL3
Figure I b. Energy balance in a GHE solar drying system
Mechanical stirrer
DRYING PERFORMANCE
Figure.l. shows how a combined solar and biomass energy is used in a drying
process in a GHE solar dryer (Manalu, I 999), Several types of GHE dryers have been constructed and tested and the results are described below. Figure.2. shows an
example of simulation results of a GHE solar dryer for coffee berry drying. For this
purpose the capacity used was 3 t wet coffee berries. In this simulation hot water was also supplied during the day as indicated by Tw. and the achieved room temperature
was slightly above 40 C while the black plate ｴ･ｭｰ･ｲｾｴｵｲ･＠ peak lied about 70 C . This indicates the need to operate full capacity of the blower to re-circulate the drying air within the chamber and at an appropriate interval the air may be disposed to the outside environment.
Vibrating Racks
A prototype tested for fermented cocoa beans drying in Bogor. Indonesia had -used vibrating racks with the main purpose to provide mixing action so that the sticky beans can be separated one from another to improve drying (Nelwan.1998), The dryer had a floor dimensions of 3.27 m x 3.27 m. equipped with an auxiliary heating unit and three 80 W blower unit. two at inlet and one at the outlet. The height of the structure was 1.98 m on one side and 2.73 m on the other. In addition a blackened steel plate was installed at the upper position inside the structure leaving 0.47 m clearance for inlet air ducting to enhance the thermal performance
Test results showed that using this system with an initial loading of 228 kg (60.4%wb) of wet cocoa beans could be dried to 6.7%wb in a total of 40 hrs. with some resting time during the night. Under this condition, the average temperature and RH were 45.2 C and 35% respectively. The total drying efficiency. 'ld as calculated using eq.(l) 18.4%.
m,Cp, (Tcr - Tpi)+m. t.Hfg
11'-
-Ip.
+ l(t)Arjed
(dmr I dt )Cr (I)Where mp. is the mass of the product dried (kg). Cpp• heat capacity of the product
(Jlkg K), Tpr, is the final temperature of the product (K), Tpi, initial temperature of
the product (K), m., total amount of evaporated water from the product (kg), t.Hfg,
latent heat of evaporation (kJlkg), Pw, electric power input (kW), 1(1), solar
irradiation (kW/m'),
e
d drying time (h), dm,ldt. combustion rate (kglh), Cr, calorificvalue of fuel (IJlkg), and .Ar, effective drying floor area (m')
The total specific energy. Es, a parameter defined as the ratio between the total input energy both from solar and commercial energy and the total amount of
evaporated moisture li"nm 1h(' beans can also be used to compare the drying performance of artificial dryers.
[p"
+ J(t) I\r]O,; + (dmr I titler
Es= --- (2)
111"
Using this parameter it was found that for the above GHE solar dryer test. the total energy required 10 evaporate moisture from the beans was 12.90
Ml/kg.(Kamaruddin el aI, I <)t)7. Nchvan. 1(98).
'""'
N
E
150,00
- -
Tp
«()
--
ｾ＠
100,00
' - '
...
Tr(C)
o(!
50,00
'""'
u
' - '
•
Tw«()
E-<
0,00
0 ...JJ
ru
ｾ＠ ::r"
"
" "
-
I<W/mA2
r-'l fl1 ::r ...JJ
)/1D
[image:5.541.62.434.266.462.2]Time (h)
Figure.2. Simulation rcsui1s of Robusta coffee berry drying at 3 t wet load.
Drying Bin with Mechanical Stin'cr
Using the same GHE dryer as described above. a trial test to overcome the
sticky beans by means mechanical stirrer had been conducted (Manalu, 1999). In this
test a cylindrical drying bin m<lde of perforated aluminum sheet was installed at the center of the chamber (see Figure. I ). A rotating anus made of steel was used as stirrer which rotate at 2.5 RPM intermittently. The stirrer was driven by 1.5 HP
electric motor equipped with a reduction gear unit to reduce the rotation down to a
required RPM level. From this test it was fr,und that the new drying method using stationary bin with stirrer had improved the specific total energy for drying to 6.2
MJlkg moisture and total drying efficiency of 46% as also shown in Table L
(Kamaruddin, el al.1998). The drying time of the latter design was between 32 to 33
II
II
ＧＬＢｾＢＮＺｩｴＬＬﾷ＠ ｾＮＧ＠ A tt!sults indicated that the dried beans fell into the first quality of
/',., ; ｩＮ｟ＢｴｾＮｴＺ＠ which means the A grade and B grade were mixed to form one AB grade,
<" .-:ommon practice in grading system of Rajamandala Cocoa plantation in Bandung, West Java. The quality achieved was better than the drying test using rectangular bin of the previous study conducted by the authors (Nelwan. 1998).
Table I. Comparison between the conventional solar drying and the GHE system
Commodity Drying Drying Load
". "
Auxiliary Source: Tempera time (kg) % (MJlkg heat sourceture (C) (h) water)
A.GHE
System
I. Cocoa
a. Lab test 1 50 40 228 18.4 12.9 kerosene Ndwan(I997) b. Lab lest 2 49.2 32 400 55 5.2 kerosene Manalu(I998) c. Field test 45.8 43 190 (8 14.4 charcoal Kamaruddin( 1998)
1. Robus/a coffee 37 58 1114 57.7 5.5 none Dyah (1997)
3. Fanilla pods 51 52 52 7.5 · ,""""," Mursalim( 1994)
4. Seeds Kamaruddin
a. Chilli 40 4 1.6
·
·
none (1995) b. Cucumber '0 9.5 5.' · · none5. Fruits
a. Papaya 39 33 '0 10.5
·
'00'
Tahir(I998) b. Banana 40.6 II 18 9.7·
none Mirza( 1997) c. Banana 2 n.a. 57 25 11.1 19.2 no", Somchart (1997)ＶＮｾｯｯ､ｳ＠
a. Bayur 39.3 158 728 8.1 25.8 Charcoal Suhdi( 1996) b. Kemiri 48.5 96 780 · none Efrida(I995)
B. Conventional
System
I. Coffee beR)' 44 70 773 21.1 11.6 wood< T ryono( 1996) 2. Cocoa 38 108 5000 10-20 n.a. wood, Utomo( 1996) 3. Banana 1 n.B. 44 360 15.8 14.9 LPG Somchart (1997)
Coffee BelT)' Drying
[image:6.551.87.510.176.501.2]Table 2 . Cocoa drying at Rajamanda1a estate. Bandung, West Java ( Utomo and T arigan, 1997)
Type of bin Flat bed Flat bed (rectangular) Flat bed
Parameter (Vertical (rectangular)
cylinder)
Wood fuel Wood coal 155 m sola,.
collecto,. witll
Ileal excllanl.er
I. Initialload(kg) 10000 5500 5500 5500
2. Initial m.c. (%wb) 68 74 74 66
3. Drying tem rature(C) 60-55-50 50 55 43-48
4. Average RH (%) 50 50 50 50
5. Drying time (h) 33 57 66 42.5
6. Dried product (kg) 3500 1870 1870 1870
7. Dried cocoalinitialload (%) 35 34 34 34
8. Electricity (kWh) 134 85 82 65
9. Additional ｨ･｡ｴｩｮｾ＠
11.3 5
a. Fuel wood (m )
.
b. Coal (kg) 900
.
c. IDO (liter) 884
10. Energy ettlciency(MJ/Kj)* 16.8 19.57 16.9
•
The specific energy IS the ratio of total Input energy (including solar energy) to the total amount ofwaler evaporated from the product.Test results with several bed depths had indicated that the highest drying efficiency was attained at 57.7% when the bin was loaded with 1.1 tons, OJ m in bed depth, of wet coffee berries. When the specific energy
was
calculated using eq.(2) in terms the total input energy, the resulting value was 5.2 MJlkg water evaporated and reduced to 0.15 MJlkg water in terms of only electric energy input. During this test the average solar radiation of 525.2 W/m2 producing average chamber temperature during of 38 C, and RH of 45%. The total drying time was 72 hours when the final moisture reached 11.2 % wb. Table I shows reported performance of solar dryer in Indonesia and for comparison data from Somchart et al (1997) is also presented. The above results can also be compared to the current drying practice and solar drying activities in Rajamandala estate plantation in Bandung West Java as shown in Table 2.DISSEMINATION OF THE TECHNOLOGY
The basic idea of technology dissemination under the grass roots program was to provide the drying facility to local entrepreneurs or cooperatives so that they are capable in constructing. operating and administrating the facility. The beneficiaries of the facility were requested to .set aside a portion of benefits gained during the operation of the facility. Such accumulated funds will be used later to construct new facility and installed in other areas for similar purpose.
In disseminating the technology it was necessary to conduct the training of local technician to construct the drying unit. With adequate supervision. these technicians were capable to follow the drawings and finally completed the construction. Most of the construction materials could be purchased locally except for the poly-carbonate sheets and the blowers. Such training programs including the operation, maintenance of the facilities and the management aspect of the project should be provided to ensure continuity of the program.
One important aspect in the dissemination of the technology is on how to provide further guidance in creating motivation so that the manager could generously find the consumers. Probably an initial working capital should also be provided so that they can start using the facility and to demonstrate to usefulness of the facility to the would be consumers. Further assistance was also found necessary in finding the market of their products.
Simple break even analysis had shown that the GHE solar dryer was ready for adaptation test. Preliminary test result of the joint project with LIPI had indicated that the one ton solar dryer was capable to dry sliced meet or fish within two days. The installed unit which was it was equipped with auxiliary heating system is gaining its popularity since it works day and night and even during the rainy days.
Currently, in Indonesia. the government is looking back to agricultural sector as the only means to accelerate the national economic recovery. For this purpose there are 17 credit schemes are made available with low interest rates of 14% per annum to promote the application of technology at the village level. With better access and availability of fund at the village level as described above it is expected that the dissemination process for GHE solar dryer in Indonesia can be accelerated.
CONCLUSIONS
ACKNOWLEDGEMENTS
The authors wish to thank the University Research Council of the Directorate General of Higher Education of Indonesia for providing grant under Research Contract No.032IHTPP-IIIURGEl1996 to accomplish most of the research work.
Without further support from the Japanese aDA for grass roots program, local
governments and also from the Indonesian Institute of Sciences (Puslit-KIM-LIPI). the application of the GHE drying technology could not be continued to its present stage for practical application.
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